Have checked Android O Features? If not, then do click here to know Android O Feature.

Android O has some advanced feature which will change your mobile using experience. The Customized navigation bar is one of them. Android O's custom navigation bar feature will let you customize the navigation bar as per your need. Some people on XDA found that custom navigation bar feature is also available for Nougat users, and you also don't need to root your phone to get this feature.

Below is the app link which will let you customize your navigation bar like, Android O.